This invention relates to microporous elastomeric compositions and methods of making such compositions. More particularly, the invention relates to a method of making reticulated microporous elastomeric structures having interconnected networks of cavities. The material produced by the method has the property of high liquid retention and is further capable of self-metering liquids upon the application of pressure.
Microporous elastomeric materials having interconnected cellular networks are used for various purposes including retentive liquid dispensing rollers, pads and the like which are used, for example, in the printing industries. These liquid filled microporous materials have also been utilized for other applications, such as lubrication. The material may also be used without liquids for various applications, such as filtration and shock absorption. It is well known that microporous materials may be made by using polymeric starting materials and employing void formers to provide porosity therein. The resulting material may then be processed into specific shapes. However, such materials and methods of production have proven to be complex and uneconomical, as well as being limited as to function and application.
In the past, there have been attempts to produce porous profiles which function well for the user and further meet manufacturer's criteria of economy, ease of manufacture, and broad spectrum composition and application. For instance, U.S. Pat. No. 3,253,542 (McDonough) discloses an improved inked roller. However, the process requires a compatible plasticizer for the polymer to form a plastisol. And, the plastisol must be condonable with the filler liquid which limits applicability. The forming process is also time consuming.
U.S. Pat. No. 4,226,886 (Lakes) discloses a microporous structure with an improved reservoir system. However, the materials must be heated to a molten state, and the process includes a mixing step which is time consuming and further limits the choice of components. The material provided thereby also exhibits a skin on its outermost surface which reduces performance.
Despite the need for a microporous elastomeric material for retaining and self-metering liquid, and a method of preparing such material which is economical and simple to practice, and which overcomes the limitations of the prior art, none insofar as is known has been proposed or developed.
Accordingly, it is an object of the present invention to provide a composition for use in elastomeric microporous structures, and a method of making such structures, which have good liquid retention and metering properties, which can be produced from a wide variety of materials, and which can be used with a wide variety of liquid systems.
It is a particular object of the invention to provide a composition and method of making elastomeric microporous structures which do not require plasticizers or high temperature processing. Furthermore, it is an object of this invention to provide elastomeric microporous structures, and a method of producing such structures, suitable to reservoir and meter liquids, by employing polyfunctional compounds.
Finally, it is an object of this invention to provide microporous elastomeric structures and methods of making such structures in an efficient, rapid manner, and which can be formed into specific configurations or profiles by various methods.